Introduction

A digital preservation strategy is a well-considered and documented approach to the preservation of digital objects. For collecting archivists, the purpose of such a strategy is to ensure that access to the born-digital archives accessioned by a repository can be maintained indefinitely. For repositories responsible for personal digital archives this will probably include material created on long-past, recent, current and future computers and devices. This is a major challenge for digital archivists because the technological landscape evolves so rapidly: new hardware, software and removable media are developed and adopted on a regular basis, and new versions often only have limited backwards compatibility. Obsolescence therefore poses a major threat to the survival of digital records and must be addressed in a preservation strategy.

Digital archivists must also be able to demonstrate to researchers that a preserved digital object is authentic: that no accidental or intentional changes have occurred; and that the stated date of creation or receipt, identity of the author and process that created the object are all verifiable. Preservation strategies are all based on the principle that the preserved digital object should be identical in all essential respects to the digital object which left the creator's computer or other device. This means that it is important to understand what is 'essential' in order to protect those aspects of a record which are essential and to measure the success of preservation interventions.

Numerous approaches, all with slightly different emphases, have been discussed in the digital preservation community. The two principal strategies are migration and emulation, although within each there are further subtle variations on the basic approach. A number of other distinct approaches have also been proposed. This chapter of the Workbook examines currently proposed digital preservation strategies and assesses their usefulness in relation to personal digital archives. It also explores some of the principles which inform each approach and some of the practical steps necessary to implement a preservation strategy.